If we look at the way Tituba reacts to being questioned (actually, it's more in response to being threatened) we can see that people will say whatever they think is most likely to save their lives.
Tituba does not really think she has done anything wrong. We can see that by how she appears pretty calm at first. But then when they start talking about hanging her, she changes.
She starts to say things she does not really believe. She says that someone else is witching the girls, and she starts to name names.
So this shows that when people are desperate, they are likely to lie to save themselves.